1. Field of the Invention
The present invention relates generally to asynchronous transfer mode (ATM) networks, and more specifically to an ATM network node wherein a plurality of servers of different classes are examined in a round robin fashion to forward buffered cells according to the frequency weights allocated to their service classes.
2. Description of the Related Art
Weighted round-robin cell multiplexing is described in a paper titled "Weighted Round-Robin Cell Multiplexing in a General-Purpose ATM Switch Chip", Manolis Katevenis et al., IEEE Journal on Selected Areas in Communications, Vol 9, No. 8, October 1991, pages 1265 to 1279. According to this prior art, ATM Cells of different traffic (or service class) are stored in corresponding buffers and counters are associated respectively with the buffers. Different values of frequency weights are loaded into the counters corresponding to the service classes. In a round-robin fashion, a cell is forwarded from each buffer until the associated counter is decremented to zero. At the end of a round robin cycle, all the counters are reset and the frequency weights are reloaded into the counters to begin a new cycle.
However, the arrival of cells in a rapid succession would form a queue in a buffer if the other buffers are also receiving rapidly arriving cells. When this occurs, the counter is decremented to zero and the stored cells must wait for their turn until the next round robin cycle begins. If these cells are of the type which must be processed on a real-time basis, delays caused by the weighted round robin multiplexing cannot be ignored.